The programming language is called Lua , it is not officially abbreviated.
Lua is a generic word for Moon in Portuguese. The language is so named because the previous programming language in PUC (at an early stage of development) was already named SOL for a simple object language. And since SOL means Sun in Portuguese, its successor is named Lua for fun.
An interesting backronym was invented by the Lua community to, ironically, explain that Lua is not an abbreviation: LUA will stand for the Lua accident.
Historically, however, the LUA has been abbreviated in Portuguese. This once meant Linguagem para Usuarios de Aplicação (Language for app users). However, the abbreviation was never used in the documentation in English, because it would be difficult for non-Portuguese speakers to understand.
Microsoft, on the other hand, unfortunately uses the acronym LUA to refer to the most privileged user account. This concept has nothing to do with the programming language, but contributes to a certain confusion.